This work is the continuation of a systematic and detailed investigation of the repertoire of genomic variation harbored by a single mammalian species--the mouse Mus musculus. Genomic libraries constructed from a set of inbred and characterized strains of mice will serve as the basis for three distinct investigations: Gene conversion: The tandemly duplicated adult Beta-globin genes of the C57BL mouse, Betas and Betat, are over 99% homologous as the result of a gene conversion. The hypothesis that homology has been maintained by repeated gene conversion will be tested by cloning and sequencing the adult Beta-globin genes from other strains of mice that have Beta-globin gene clusters similar to, but not identical with, of C57BL. The sequence of these different converted intervals will clarify how the conversion process acts in rectifying genes by providing examples of very recent conversions, whose details have not been obscured by unrelated mutations. Recombination and rearrangements within Alpha-globin gene families: Even the simplest model for the evolutionary relationship of the eight Alpha-globin haplotypes identified in the mouse involves, in addition to ordinary replacement changes, two different instances of either gene conversion or gene silencing, and one instance of extragenic recombination characterization of these eight haplotypes will define the details of the recombinations and rearrangements by which they were derived. Concerted evolution of LINE elements: The concerted evolution of the long interspersed repetitive elements (LINEs) may reflect the fact that these elements are continually being strewn about the genome, through an RNA intermediate, from a small number of transcriptionally active "mother" LINEs. A putative nascent, newly inserted LINE element will be used as a source of hybridization probes to isolate, under conditions of high stringency, other very homologous and hence recently dispersed LINEs. Fragments from the single-copy DNA that flanks these elements will be used as insertion-site probes to see whether, as expected, the mouse species is polymorphic with respect to putative nascent LINEs. Finally, these same probes will be used to screen a cDNA library for a transcript of the "mother" LINE.